πK scattering in full QCD with domain-wall valence quarks

We calculate the π+K+ scattering length in fully-dynamical lattice QCD with domain-wall valence quarks on MILC lattices with rooted staggered sea-quarks at a lattice spacing of b = 0.125 fm, lattice spatial size of L = 2.5 fm and at pion masses of mπ ~ 290, 350, 490 and 600 MeV. The lattice data, analyzed at next-to-leading order in chiral perturbation theory, allows an extraction of the full πK scattering amplitude at threshold. Extrapolating to the physical point gives mπa3/2 = -0.0574 ± 0.0016+0.0024-0.0058 and mπa1/2 = 0.1725 ± 0.0017+0.0023-0.0156 for the I = 3/2 and I = 1/2 scattering lengths, respectively, where the first error is statistical and the second error is an estimate of the systematic due to truncation of the chiral expansion.